The cheapest and possibly the best house batteries are two golf cart batteries wired in series. You do need extra height in your battery compartment (about 1" more) to fit. You also have to check and add water several times a year. These can be bought at Costco, Batteries Plus, etc for about $100 each.
If you don't have room or you don't like checking water, AGMs are the next best choice. Windynation has them on Amazon for less than $200 each.
And finally lithiums offer twice the usable capacity, but typically require a change to your converter's charger and a change to your BIM. They cost 3-4 times as much as AGMs but provide twice the power. The charger and BIM upgrades will also add $5-600 to the overall cost.
David
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